Understanding Hot Water Chemistry
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
TM
A L o n z a B u s i n e s s
5660 New Northside Dr. NW
Suite 1100
Atlanta, GA 30328
PoolSpaCare.com
Understanding Hot
Water Chemistry
By: John D. Puetz
Director of Technology
Advantis Technologies
A Lonza Business
Leisure Time®, the Leisure Time® logo, GLB®, the GLB® logo, Oxy-Brite®, Rendezvous®, Applied Biochemists®, the Applied Biochemists® logo,
Ultima®, Quantum Biochemical®, and Aqua Silk® are registered trademarks of Arch Chemicals, Inc. Advantis Technologies™, Quantum™,
Robarb™, Spa Specialties™ and Advantis™ are trademarks of Arch Chemicals, Inc. Advantis Technologies is a business of Arch Chemicals, Inc.
© 2012 Arch Chemicals, Inc. , now a part of Lonza. All rights reserved. Unauthorized duplication prohibited. # ADVSPABOOK
About the Author
John Puetz is the Director of Technology for Advantis Technologies, now a part of Lonza.
Having served for more than 35 years in the pool and spa industry, John has been a
flagship member of the Advantis development team and has been instrumental in bringing many
of its most innovative products to the marketplace.
In addition to his duties with Advantis, John conducts pool and spa water chemistry
seminars throughout the country for retailers, industry groups and health department
personnel.
John has also served on numerous advisory panels throughout the industry including:
• Member, Board of Directors, National Swimming Pool Foundation
• Past Chairman of the NSPI (National Spa & Pool Institute) Technical Council
• Past Chairman of the NSPI Chemical Treatment & Process Committee
About Advantis
Advantis Technologies, part of the Lonza Microbial Control ProDealer Channel, produces some
of the most popular pool and spa water care products on the market today in its Alpharetta, GA
plant. From the industry’s first non-chlorine shock, GLB® Oxy-Brite® non-chlorine shock oxidizer,
to the latest in enzyme products and chlorine-free spa care, Advantis has always been on the
cutting edge of pool and spa water care technology while consistently offering high quality
products.
The Advantis™ family of swimming pool and spa chemical brands include the Leisure Time®, GLB®
pool, Rendézvous® Spa Specialties™, Applied Biochemists®, Robarb™, Ultima®, Aqua Silk® pool and
Quantum Biochemical® brands.
Visit Advantis on the web at PoolSpaCare.com for more information.
TM
LeisureTimeSpa.com
RendezvousSpa.com
GLBPool.com
AOUA SILK
®
Robarb.com AquaSilkPool.com
AppliedBio.net
TM
UltimaPoolSpa.com QuantumPool.com
Understanding
Hot Water
Chemistry
by
John D. Puetz
Director of Technology
Advantis Technologies
A Lonza BusinessTable of Contents PAGE INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 CHAPTER ONE-PHYSICAL FACTORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 FILTRATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 TURNOVER & CIRCULATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 OTHER FACTORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 CHAPTER TWO-CHEMICAL FACTORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 pH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 TOTAL ALKALINITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 CALCIUM HARDNESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 STAIN PRODUCING MINERALS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 TOTAL DISSOLVED SOLIDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 CHAPTER THREE-BIOLOGICAL FACTORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 DISINFECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Chlorine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Bromine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Biguanide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Ozone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Mineral Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 SHOCK TREATMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Super chlorination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Shock oxidation treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 ALGAE CONTROL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Introduction INTRODUCTION Notes: This book is written to help provide you with a better understanding of how you can assist your customers with getting the most out of their spa/hot tub. Humans have been bathing since the earliest days. From ritual bathing to simple relaxation, we have frequently used water not only to cleanse ourselves but for relaxation and recreation as well. Perhaps your customer is new to owning a hot tub in which case congratulations are in order. Or perhaps they have owned a tub for years. Regardless of which best describes your customer, this book will help guide you through what you need to know to help them get maximum enjoyment and performance from their tub. Definition of a spa or hot tub... A spa or hot tub can be simply defined as a relatively small body of water, rarely exceeding 500 gallons for residential use, that contains hot (95 –104ºF) water that is circulated in a vigorous fashion and is further agitated by the injection of “air blowers” into the water stream. The result is hot, turbulent water that at once soothes, relaxes and invigorates the bather. But it is these same qualities that require us to manage these waters differently. We used to think that they were most easily operated as small swimming pools. Experience has proven that approach to be wrong. Treatment challenges Three factors contribute the most to our challenges in properly treating a spa or hot tub: • High water temperature: Hot water creates several conditions that increase the stress on the water and thus on treatment needs. Firstly, the warm water causes the pores on a bather’s skin to dilate thus allowing the warm water to carry away some of the natural skin oils. This increases the waste products in the water and places stress on the sanitizing system being employed. Secondly, the warm water increases the evaporation rate. It is important to realize that as water evaporates it will leave behind all of the minerals and other materials dissolved in it. We will explore this in greater detail later on. • Heavy bather loads: Due to the relatively small water volume the use of a tub by even a small number of bathers creates a significant impact on the water. Consider that two people in a 500 gallon spa are the equivalent of 80 people in a typical backyard swimming pool. This results in large accumulations of bather wastes in a very small volume of water. The water 3
Introduction
is treated to control these wastes and therefore it is not the volume of Notes:
water that determines how much we need to treat but the volume of bather
waste or the bather load. This is a critical reason why hot tubs cannot be
treated as if they were small swimming pools.
• Turbulent water: The rapid movement of spa/hot tub water leads to
increases in evaporation, sanitizer depletion, increased concentration
of bather wastes, possible foaming and can even alter other chemistry
factors that increase corrosion of equipment. Additionally this rapid water
movement actually leads to a “scrubbing” action on bather skin that results
in removal of dead skin and debris as well as removing protective oils which
can result in dry skin complaints.
This manual will introduce the basic factors of spa and hot tub water
chemistry and management. In addition to explaining water chemistry, this
reference is intended to address the most important aspect of proper
maintenance — how to get the most enjoyment and ease of use.
As spa/hot tub professionals, it is important that we always keep in mind
that our primary responsibility is not the adding of treatment chemicals or
the operation of equipment, but rather, to use these tools in the overall goal
of providing clean, clear and healthy water. After all, our performance as a
professional is measured largely on how well we prevent problems and keep
the water safe and inviting.
Our role in the industry is to help assure that clean, clear water is delivered.
In spa management this has not always been an easy task. Given the
challenges detailed above spa owners often wrestle with frequent and unusual
problems in keeping water clear, clean and odor free. This has led to the
introduction of a wide variety of novel and often questionable treatment
programs and products. Much confusion has resulted in how these products
work, if at all. Customers tell us they are seeking more “natural” or user-
friendly products because they are frustrated with the complexity of what
they are using and the confusing information they get on how they should be
treating their spas.
The goal of this manual is to help you do the best job in keeping your
customers positive about their spa experience. This can best be accomplished
by providing information that will help simplify how spa maintenance should
be carried out and eliminate the conflicting and complicated guidance they
may have received in the past. The first part of the book will highlight the
basic factors of spa water care: Physical Factors, Chemical Factors, and
Biological Factors.
Although many of these points will likely come as a review for you, the
purpose here is to provide this information in a centralized resource that will
not only help you manage spa chemistry on the job, but more importantly,
help you to gain and keep loyal and satisfied customers.
4Introduction
BASIC FACTORS Notes:
Three basic factors are involved in spa operation. Each of these, when
properly managed will work with the others to provide clean, clear, safe and
inviting water. These factors are:
A. Physical factors such as filtration and turnover
B. Chemical factors which include scale and corrosion control
C. Biological factors including disinfection and control of
bather wastes and odors
Each of these factors requires management primarily to control
what is in the water. Even before we put water into a spa it will contain
contaminants and solids that will require filtration in order for the water
to start out clear. Additionally, the water may contain naturally occurring
minerals such as iron that can stain surfaces or calcium that can cause cloudy
water or scale. Once the water is in the spa the bather and resulting wastes
become a critical area of focus in our treatment.
A clear understanding of these factors and what is involved in each is vital to
understanding how they can be used to manage the water. To do this we will
review each in detail.
5Chapter One – Physical Factors
CHAPTER ONE - PHYSICAL FACTORS Notes:
The physical factors include filtration, turnover and
circulation of the water. In addition there are other
factors including the control of oily wastes left behind
by the bathers and the maintenance of equipment as well
as care of covers and appearance that must be tended to. Each factor plays
an important role but is frequently overlooked in the importance it plays in
being able to completely enjoy the spa experience.
When faced with a problem in the hot tub or spa, we have a tendency to
immediately look into the water chemistry factors as a likely cause. Cloudy
water, for example, causes us to question water chemistry when the problem
may simply be due to a filtration issue. The management of the physical
factors should never be discounted in the value it provides to keeping water
clear and even in keeping the water properly sanitized. To really consider how
important filtration is to keeping water clean just try to imagine how difficult
it would be to keep the water clear without a filter.
Keep in mind that poorly filtered water will contain large amounts of physical
waste that will dramatically interfere with sanitizer performance. Another way
to think of it is that properly filtered water will allow for maximum benefit
from lower levels of sanitizer. Therefore a properly operating filter is essential
for your customers who may be seeking a reduction in the level of chemicals
they want to employ to keep their water clean.
I. FILTRATION
Filtration is the term used to refer to the mechanical cleaning of the water.
It is a key element in all water maintenance that is frequently overlooked
in its importance. When operating properly, a filter will remove virtually all
particulate matter from the water. These particles of dirt and debris are the
result of environmental fallout or are left behind by the bathers and, when
not properly filtered out, will cause the water to become hazy and cloudy,
increase odors, lead to foaming problems and substantially reduce the
effectiveness of the sanitizer.
FILTER TYPES
There are three types of filters that may be used on spas: cartridge, sand and
diatomaceous earth (DE). While any of the three could be used, the most
common type is the cartridge filter and therefore, we will concentrate our
discussion on these.
Cartridge Filters
Cartridge filters consist of pleated fabric, typically
polyester, arranged in a cylinder form around a rigid core.
The fibers of the polyester trap dirt and oils as the water
passes through from around the outside of the cylinder and
is returned back through to the spa from the center core.
While not regarded as the most efficient in terms of their
6 ability to remove the tiniest particles of dirt, cartridgeChapter One – Physical Factors
filters are widely selected for their utility in spa water applications. They are Notes:
easily and quickly removed for cleaning and returned for use. If damaged
or when the cartridge wears out, they are easily and economically replaced.
Additionally they are excellent in their ability to remove oils and greases,
which we know, are a substantial contaminant to spa water.
Cartridge filters will give long and excellent service if they are properly
handled. A critical first step in keeping your cartridge operating properly is
to keep it clean. Regular rinsing of the cartridge will help in removing large
debris; however, deep cleaning will not only assure better-looking water but
longer life from your cartridge as well. Deep cleaning is best accomplished by
using a cleaner specially formulated for spa filters.
Such a cleaner should be capable of removing both oily and greasy buildup,
as well as minerals such as calcium that may have been deposited on the
fabric. A good filter cleaner will contain a combination of surfactants for oil
and grease removal, as well as agents that will readily dissolve away built up
minerals.
Another way to help extend cartridge life is to keep two sets, one set in
use and a clean set ready to go. This allows you or your customer to quickly
exchange the cartridges when needed and to clean the dirty ones at a
convenient time. Once cleaned, allow the cartridges to dry before reinstalling
them. This allows the fibers to expand and fluff up thus providing more
effective filter area.
Residential spa owners frequently ask about how often they need to
completely clean their cartridges. While the answer varies depending upon
bather load and frequency a general rule of thumb would be every 30-60 days.
It is typically a good idea to at least rinse off your cartridge on a weekly basis
using a garden hose. High pressure washers are not recommended as they
tend to tear up or rapidly age the cartridge fabric.
Between deep cleanings a “spray-on” type cleaner can be used to help remove
oils and greases that would not be easily rinsed off in running water alone.
This type of cleaner is ideal for when time does not allow for deep cleaning
or for Service People who need to do routine service and want to get better
performance than they would get from simple rinsing. The use of a spray-on
cleaner between deep cleanings will help reduce the frequency of the need for
deep cleaning.
Diatomaceous Earth Filters
Diatomaceous earth filters are only rarely used on spas
and come in a variety of forms. Typically they consist of a
fine mesh fabric configured in a variety of shapes or forms
including bags, grids or screens and “fingers.”
DE is a fine white powder composed of the skeletal remains
of nearly microscopic organisms that lived in the sea
millions of years ago. These skeletons are mined from the
earth and cleaned. The powder is applied to the surface of
the fabric and acts to trap dirt as the pool water passes
7Chapter One – Physical Factors
through it. As the DE becomes clogged with dirt, it is washed off of the fabric Notes:
and replaced with new DE to begin the process all over.
While DE provides excellent dirt trapping ability, it is this same quality of
being able to filter such small particles that cause these filters to be in
disfavor for spa applications. The amount and type of debris in spa water is
generally of such a nature as to make these filters impractical, as they tend to
clog too easily. In cases where a DE filter is used on a spa, the regular use of
a good filter cleaner/degreaser will keep the filter fabric free of oily buildup.
Sand Filters
Sand filters, as the name implies, utilize sand as the
filtering medium. Sand is regarded as a good filtering media
but because the filters tend to be bulky in size compared
to cartridge and DE filters, they are not often used for spa
applications.
II. TURNOVER & CIRCULATION
Circulation is the term used to refer to the process of
moving all of the water contained in a spa/hot tub. In
contrast, the term turnover is used to describe how long it takes for the water
being circulated to pass through the pump and filter. When we are managing
swimming pool water, circulation is the more critical factor as areas of slow
or poor circulation within a pool lead to poor control of algae or sanitation
problems. In spa/hot tub maintenance though turnover plays the more critical
role. Think about it for a moment. Given the way water in a spa/hot tub is
pumped, jetted and aerated, it is pretty hard to imagine all of the water
is not being circulated. More important is the need for rapid effective
filtration. We need to get the water in the tub to the filter as often as
possible to remove the solids being contributed by the bather. Unless the
water is being properly filtered and filtered often, these solids can interfere
with sanitizer efficiency and increase problems with cloudy water and
foaming.
III. OTHER FACTORS
There are several other areas that require attention in order to keep the spa/
hot tub looking inviting and ready for use. Proper control of fine particles
that would otherwise escape removal by the filter through a process known
as clarification and destruction of oily wastes contributed by the bathers
by use of an enzyme digestion will not only assure clear water but improve
sanitation as well.
CLARIFICATION
Spa/hot tub water creates large challenges for filters to remove all of the
debris that contaminates the water. It must be remembered that the amount
of waste added to each gallon of spa/hot tub water is much more than would
be added to swimming pool water. This is due both to the small volume of
water per bather and to the increased stress of high water temperature and
8 the turbulent nature of the water. While the filter, even though properlyChapter One – Physical Factors
maintained, is doing a fairly effective job it will be hard pressed to provide Notes:
maximum water clarity. Fortunately there are aids that you can employ to
help remove even the finest particles from the water.
While large particles are most easily removed by the filter it is common for
the small particles to pass through the filter and remain suspended in the
water leading to the buildup of what is commonly referred to as
microparticles in the water. These particles are so small that they simply
pass through the filter media without being trapped. To make matters worse,
these particles develop a negative electrical charge and since the charges
are all alike, they repel one another and do not clump together, which would
otherwise make them easier to filter out. The addition of a “clarifier” will
solve this problem.
A water clarifier contains a solution of positively charged particles that
when added to water will seek out the negative particles and neutralize their
charges. The particles will then clump together resulting in larger particles
that are easily filtered out. Used regularly, a clarifier will reduce maintenance,
improve filter performance and enhance the appearance of the water.
The regular use of a clarifier will assure your filter removes the maximum
amount of particles from the water thus giving your customer the best water
clarity. Using the product could not be easier.
CONTROL OF GREASE AND OILS
Hot and turbulent water are what make bathing such a relaxing experience.
But they are also the factors that create challenges in managing the water
quality. When we enter the water the warmth causes the pores of our skin
to dilate or widen which exposes the natural oils of the skin to be exposed
to the water. At the same time the rapidly moving water actually creates a
“scrubbing” action that physically pulls these oils away and into the water.
Complicating the matter is the increased rate of perspiration resulting from
the warm water. The result is a water body that contains a large amount of
organic wastes that place a tremendous stress on the sanitizer and filtration
system.
Accumulations of body oils, cosmetics and other complex bather waste will
result in the build up of these materials along the water line and in pipes and
filters. This waste causes unattractive scum lines, increases foaming problems
and interferes with the performance of the sanitizer, and generally create
problems that will affect the overall appearance of the water and bathing
pleasure.
These wastes can be most effectively controlled using enzymes. Enzymes
are widely used today in both industrial and domestic applications. Many
laundry detergents use enzymes to help in the breakdown and removal of
stains and deep-set soil. Enzymes are naturally occurring biological catalysts,
which means they help increase the breakdown rate of complex compounds.
In spa/hot tub water, specially developed natural based enzymes are used
to help breakdown complex materials like oils and grease. With regular use
they will take these very complex and difficult to control materials and break
9Chapter One – Physical Factors
them down into smaller fragments that can be readily destroyed by shock Notes:
treatment.
However, it is important to point out that not all enzymes are well suited for
spa/hot tub use. As stated above, enzymes are naturally occurring substances
of biological origin. Since they are manufactured by living organisms and
since Chlorine and other sanitizers destroy living substances, it is important
to select enzymes that can tolerate the typical sanitizer levels commonly
found in spa/hot tubs. It is also important to understand that enzymes are
highly selective in terms of what substances they will breakdown. Therefore,
one must use enzymes that have been properly selected for digestion of the
types of oils and greases found in spa/hot tub water.
Used as part of a regular maintenance program, enzymes will minimize scum
line formation and reduce the frequency for the need to clean along the
water line as well as reduce the build up in pipes and equipment. In addition,
the enzyme will help reduce the build up of these organic wastes on filter
media and thus reduce the frequency of cleaning as well as improving water
appearance.
10Chapter Two – Chemical Factors
CHAPTER TWO - CHEMICAL FACTORS Notes:
Now that the physical processes are understood, we turn
our attention to managing the chemical treatment of the
water. Proper chemical treatment is needed in order to
prevent a wide range of potential problems including scale
and stain formation, colored or cloudy water, foaming, skin
irritation, corrosion of equipment and to assure proper performance of the
sanitizer being used.
There are five chemical factors that affect water quality. These are listed
below in order of importance along with their ideal levels:
Chemical Factor Recommended Level
1. pH 7.2-7.8
2. Total Alkalinity 80-150 ppm
3. Calcium Hardness 150-400 ppm
4. Stain Producing Minerals Absent
5. Total Dissolved Solids (TDS) Max 1500 ppm
The first three, along with the temperature of the water, determine the overall
“Water Balance.” Water balance is the term used to refer to the tendency of
the water to be either “scale forming” or “corrosive or aggressive.” Water that
is referred to as having scale forming tendencies is one that is considered
likely to suffer from problems related to high pH, high total alkalinity,
hard water (elevated calcium level) or combinations of these. When these
conditions are present, it is common for the water to be cloudy and for scale
to form on surfaces especially heaters. Corrosive or aggressive water is most
commonly associated with chemical factors, which is the opposite of those
above, and results in corrosion of equipment such as heaters.
Maintaining proper chemical levels or providing good water balance can easily
prevent these problems and others.
I. pH
pH is the term we use that tells us how active an acid or base is in the water.
It is the single most important chemical factor in spa/hot tub chemistry.
Because of the high water temperature and rapid rate of water movement
a pH even slightly outside of the normal range will have a profound effect
on water quality and the likelihood of scale formation or corrosion. pH is
measured on a scale from 0 to 14 with 7 being neutral. A pH value between
0 and 7 is considered acidic with 0 being the greatest acid activity and
getting weaker as it approaches a value of 7. A value between 7 and 14 is
considered basic with 14 being the greatest base activity. Another word for
basic is alkaline; however, this is not to be confused with total alkalinity
and therefore we will use the term base in this discussion as pH and total
alkalinity is not the same thing.
11Chapter Two – Chemical Factors
The pH is best kept in the range of 7.2 to 7.8. When pH remains below 7.2, Notes:
the water is considered to be corrosive. This means corrosion of metallic
components in equipment such as heat exchangers will result. In addition,
if you are going to use Chlorine to sanitizer the spa/hot tub water it will
be more difficult to keep the Chlorine at the proper level because at pH
levels below 7.2 Chlorine is much less stable resulting in the consumption
of larger quantities of Chlorine than would be used at normal pH levels. It
is interesting to point out that while the Chlorine level is harder to keep at
the desired level, the Chlorine itself is actually more effective as a sanitizer
when the pH is low. In fact as pH goes up the ability of Chlorine to control
microorganisms actually goes down. This will be discussed in more detail in
the Disinfection section of this book.
Maintaining the pH higher than 7.8 will increase the tendency to form
scale or cloudy water. Calcium, the major component in scale, is a relatively
unstable mineral and when the pH is high, the calcium is not as soluble
and it will have a greater tendency to precipitate or “fall out” of solution
resulting in cloudiness or scale. This is even more important in spa/hot tub
water as the high water temperature actually increases the rate of scale
formation. (See section on Calcium Hardness) High pH will also reduce
Chlorine effectiveness, in those spa/hot tubs using Chlorine, resulting in the
need to maintain higher Chlorine levels to achieve maximum sanitization.
The easiest means of controlling pH for most of your homeowner customers
would be through the use of a “pH buffer” product. These unique products
can be added to the water whenever the tub is drained and refilled with fresh
water. When added they will “lock” the pH into the desired range and keep it
there for up to three months. When present in the water they act as buffers to
maintain pH in the desired range by automatically neutralizing those things
that would otherwise raise or lower pH. By using one of these products your
customer can all but eliminate the need to make regular adjustments to the
pH. This reduces the difficulty often associated with water maintenance where
“overshooting” the desired pH with acids or bases is a common complaint.
HOW TO ADJUST pH:
Some of your spa/hot tub owners may prefer to control the pH and other
chemical factors themselves. In fact, if you are servicing the commercial spa/
hot tub market the stresses of heavy use may lend itself to using separate
acids and bases to adjust pH. Making these adjustments is easy using spa up
or spa down in either liquid or dry forms.
If the pH is low add spa up. It is suggested that consumers or those with
small water volume tubs use a liquid spa up as it is a gentler formula and they
will have more comfortable control of the adjustment and are less likely to
over shoot the desired pH range. Larger tubs or commercial facilities will get
more control with the concentrated dry spa up.
12Chapter Two – Chemical Factors
If the pH is high add spa down. Here too it is suggested that the liquid Notes:
versions are better for small tubs or consumers and the dry forms are
better used buy commercial facilities or larger consumer tubs.
Regardless of which form you select or if raising or lowering pH it is best to
add small quantities each time, allow the water to completely mix and come
into equilibrium before retesting and then adding an additional dose as may
be required. Attempting to make large adjustments in one dose will often lead
to frustration of driving the pH too far in one direction or the other.
II. TOTAL ALKALINITY
Changes in the pH of the water can be caused by many factors but the most
significant cause is the sanitizer used. Since the sanitizer is likely the
most frequently added chemical, it will have a powerful impact on pH and
overall water quality. Changes in pH due to sanitizers or other factors can be
minimized and controlled by the proper maintenance of the next chemical
factor, total alkalinity.
Total alkalinity refers to the ability of the pool water to resist a change in
pH. The key purpose total alkalinity serves is to help manage or control the
pH in the water. It does this by acting as a buffer so that when materials are
added to a spa that would cause the pH to go up or down these changes are
controlled and do not result in severe changes to spa water balance. When
a substance is added to spa water that could affect the pH, total alkalinity
will react to neutralize it and help keep the pH in the desired range. Total
alkalinity does not determine what the pH will be, but rather acts to help
keep the pH in the range desired.
Total alkalinity is measured in parts per million (ppm) using a total alkalinity
test kit or test strips. Total alkalinity is best kept in the range of 80-150 ppm.
When the value is less than 80 ppm, the water can become aggressive and
the pH can swing easily upward and downward and back again making it very
difficult to control. If the value is higher than 150 ppm the water can become
cloudy and scale forming and the pH will tend to drift upward.
13Chapter Two – Chemical Factors
HOW TO ADJUST TOTAL ALKALINITY: Notes:
In adjusting total alkalinity downward, the same acids used to lower pH,
are employed. When reducing total alkalinity, it is best to add only a small
amount of acid at any one time as opposed to making large adjustments
rapidly. Once the acid is added allow the water to circulate completely and
wait at least four (4) hours before retesting and making the next addition
if needed. Adding too much acid at once may result in lowering the pH so
severely that corrosion of equipment would result.
When raising total alkalinity Sodium bicarbonate or Alkalinity Increaser is the
product of choice.
To use:
1. Only use if total alkalinity is below 120 ppm.
2. Add no more than 1 oz at a time.
3. Allow mixing for at least 30 minutes.
4. Recheck total alkalinity and repeat dosage above if needed.
III. CALCIUM HARDNESS
The sum of all the calcium dissolved in water is referred to as the calcium
hardness. Years ago, water with high levels of calcium was described as being
hard to wash in. This is because water with high calcium levels does not
clean clothes as well as water of a lower hardness. The term hardness is now
used only to refer to the level of calcium. The term soft water refers to water
with little or no levels of calcium.
Calcium is important in spa/hot tub chemistry since high levels are
particularly unstable in warm water such as typical of spa/hot tubs. As water
temperature rises, calcium becomes more likely to precipitate out of solution.
The result can be significant scale formation in heaters. Calcium is actually
more soluble in cold water, which is why scaling of heater equipment is so
common. (Picture the inside of a tea kettle.) Calcium also becomes more
unstable when the pH or the total alkalinity rise above the normal levels.
Scale formation can be a serious problem in spa/hot tubs. When scale forms
on heaters the result will be inefficient heat exchange due to the insulating
properties of the scale. The scale formation in turn leads to higher energy
consumption and costs or even a melt down of the heater tubing itself due to
excessive heat.
Customers with tubs heated electrically will frequently complain of finding
“chips” lying in the bottom of their tubs after they have used them and
turned off the blowers and jets. This is not always a bad thing but it
can be controlled. What happens is during periods of non-use where the
circulation pump runs slowly as needed to keep the water at a temperature
higher than ambient but high enough whereby the water can be heated
to bathing temperature quickly, the slow water movement over the heater
allows for some scale to be deposited on the heater element. When the unit
is started up for use and the blowers and jets increase the water flow over
the elements the natural abrasive action of the water actually strips the light
14Chapter Two – Chemical Factors
scale formation off of the element. When the unit is again turned down any Notes:
chips that did not get filtered out settle to the bottom where your customer
sees them. You can explain to them that this is better than having the scale
build up and cause heater failure later on. You can also recommend using a
sequestering agent to prevent the formation of the scale. (See below.)
With all of the difficulties calcium can cause, it would seem logical to use soft
water in the spa/hot tub. However, this is not the case! While high calcium
levels can cause problems with cloudy water and scale, soft or low-calcium
water is also of concern. Such water is aggressive and will actually attack
metal fittings and heat exchangers resulting in destruction of the fittings or
pinhole leaks in the heater. When such corrosion occurs, it is also common for
stains to appear on surfaces.
HOW TO INCREASE CALCIUM LEVELS:
Calcium content is best in the range of 150-400 ppm with 150-250 ppm being
ideal. Unlike pH or total alkalinity, however, both of which can be raised or
lowered with reasonable ease, calcium levels cannot.
Adding calcium chloride to the water easily raises calcium levels. Conversely,
there is no simple chemical addition that can be made that will reduce
calcium hardness. The only way to reduce calcium hardness levels is through
dilution with water of a lesser hardness. Over time, calcium hardness will
naturally increase in spa/hot tub water due to evaporation.
To use calcium chloride:
1. Test calcium level with test kit to determine how much calcium
chloride is needed.
2. Use 1 oz of calcium chloride to raise calcium level 7 ppm in 500
gallons of water.
3. Turn on all equipment and add required dose.
4. Run pump for 1-2 hours to assure complete mixing.
While it may be difficult to reduce calcium hardness, it is possible to control
it so that a potential problem such as cloudy water or scale formation is
prevented. The most effective way to control calcium in spa/hot tub water is
through the use of a sequestering agent. A sequestering agent is a compound
that, when added to water, will chemically bond with calcium and other
minerals to make them, in a sense, more soluble. This means that calcium
will still be present, but in a form that is less likely to cloud water or form
scale in warm water or where the pH or other factors get out of balance.
In addition, since calcium will still be in the water, you will not have the
corrosion problems or foaming you would otherwise experience with soft
water. A further advantage is that elevated levels of calcium can be tolerated
without the need to use a water softener. This becomes especially important
when the pool is located in hard water areas.
15Chapter Two – Chemical Factors
HOW TO CONTROL HIGH CALCIUM LEVELS: Notes:
A reasonable level of calcium is desirable in spa/hot tub water. However,
when levels increase they can cause problems with scale formation or cloudy
water. While this most commonly occurs at levels above 400 ppm it can occur
even at lower levels. Therefore it is best to use a sequestering agent as part
of the normal treatment program in all spa/hot tub water. Select a product
that is specially formulated to meet the demands of hot water systems. When
used according to directions it will “tie-up” or chemically bond with the
calcium to keep it in solution and prevent it from building up as scale.
HOW TO CONTROL FOAMING:
Foaming problems are fairly common in spa/hot tub water. While
foaming can be caused by a variety of factors foaming is most frequently
associated with soft water. When foaming is seen as frequent or persistent in
a particular unit it is wise to have the calcium level tested and raised into the
proper range if found to be low. Occasional foaming not resulting from soft
water such as may occur with heavy bather load or failing to completely rinse
a filter cartridge after cleaning is best controlled using a defoamer.
When foaming is noted simply squirt a little defoamer directly onto the foam
and watch it disappear.
IV. STAIN PRODUCING MINERALS
Problems of stain formation on surfaces or colored water are most often
associated with the metals iron or copper. Each of these metals can enter a
spa/hot tub by several means and will react in very different ways. One of
the most common ways these metals can enter the spa is via the fill water.
Therefore, before filling a spa/hot tub, always be certain to have the water
tested for metals in addition to the other chemical parameters. In this way
you will be better prepared to deal with the initial treatment, both water
balance and stain control.
IRON
When dissolved in water, iron is colorless but will react almost instantly with
Chlorine or other oxidizers to produce a rusty red color in water, or worse,
orange colored staining. As little as 0.1 ppm of iron is all that is needed to
result in colored water and stains. The most common source of iron is the fill
water. A second source of iron is corrosion or galvanic action taking place on
equipment. Some heaters contain iron-based components. Galvanized “heat
sinks” that are directly connected to copper heat exchange tubes are one such
source. If a corrosive condition such as low pH or total alkalinity or soft water
were to come into continuing contact with the heat sink it could corrode the
iron leading to high levels of iron in the water. A second problem with such
heat sinks directly connected to the copper can lead to galvanic corrosion
from the two different metals in direct contact. In a sense it is like a battery
where ions exchange one with the other. A good indication of these types of
problems is heavy staining in the immediate vicinity of the return line
discharge eyeball in the wall or floor of the spa/hot tub.
16Chapter Two – Chemical Factors
COPPER Notes:
A common cause of green water and stains ranging in color from blue-green
to black, is copper. Copper sources are more varied than iron. Copper can
enter the water from corrosion or galvanic activity in copper heaters and from
the source water. Copper problems are often indicated by water with a true
clear green color. Copper is also the responsible agent when hair or fingernails
turn green, not Chlorine, which is often blamed.
Corrosion of heaters that have copper heat exchange tubes results in copper
entering the water flow, which, in turn, can lead to green water or stains.
This type of corrosion is most commonly due to a chemical imbalance
discussed above under Iron and includes low pH, low total alkalinity or
low calcium hardness or a combination of these factors. As stated above
a galvanic action can take place in heaters where the copper metal of the
heater coil comes in contact with a different metal such as iron. At points
where these two dissimilar metals are in direct contact, both metals can
break down and find their way into the water. This particular problem is
best solved by use of a “dielectric” coupling. This is typically a pipefitting
made from a ceramic or similar inert material that is placed between the two
metal components and prevents them from coming in direct contact with one
another.
Copper can also come from the source water and will either be present as a
normal component of the water or on a periodic basis. Many municipal water
systems rely upon reservoirs for their water supply. These reservoirs frequently
suffer from algae outbreaks and the algae are treated with copper. The copper
level is often as much as 1.0 ppm, and if you fill or add water to your spa/hot
tub, it will be green and could result in staining.
17Chapter Two – Chemical Factors
HOW TO CONTROL METALS IN THE WATER: Notes:
The best time to treat for metals in the water is whenever you first fill the
spa/hot tub or drain and refill the unit. This will assure your customer of clear
water free of any staining right from the start. Use of a sequestering agent
each week will control metals following this first treatment.
The important thing to understand is that all metals can easily be kept from
causing problems with the regular use of a sequestering agent. As with
calcium, a sequestering agent will chemically combine with the metals in the
water and keep them from precipitating out of the water to cause staining.
The best time to use is when the spa/hot tub is being filled for the first
time, and thereafter as part of a regular preventive maintenance program. In
this way, any metals that may be present in the fill water will be tied up or
inactivated before they can cause a problem. Even if a test of the fill water
does not show any metals are present it is wise to add a sequestering agent.
Consider it is easier and less costly to prevent a problem than to correct it.
The regular use of a sequestering agent will assure that any metals that
may find their way in later, either when water is added or from corrosive
actions, will be prevented from causing staining. In other words, by adding a
sequestering agent as part of the regular maintenance program, the unit will
be protected from stains even when you did not expect metals to be present.
V. TOTAL DISSOLVED SOLIDS
Total dissolved solids (TDS) are normally the least worrisome factor when
managing swimming pool water. However, while TDS may never become a
problem in most pools, some commercial spas/hot tubs can see problems after
as little as 24 hours of operation. Residential spas/hot tubs will take much
longer to experience such problems because they have smaller bather loads
but nevertheless they will require periodic draining and refilling. Therefore
it is important to understand TDS and its role in spa/hot tub chemistry and
management.
Simply put, TDS is the sum of all materials dissolved in the water and
normally runs in the range of 250 ppm and higher. There is much discussion
over what levels are considered too high, but there is no real lower limit. TDS
is comprised of many different chemical compounds, which means that the
issue of how much is too much actually depends more on what they consist
of than how much there is. For example, sodium chloride or ordinary salt is
extremely soluble and is therefore unlikely to cause a problem, whereas, as
we have seen, calcium compounds can be a problem even at fairly low levels.
By its nature of utilizing hot, turbulent water a spa/hot tub is prone to very
rapid accumulation of excessive solids (TDS). In general, when the TDS
exceeds approximately 1500 ppm, problems are likely to begin occurring.
18Chapter Two – Chemical Factors
The hot, turbulent water causes excessive amounts of bather waste in Notes:
a very small body of water. Managing these wastes in turn requires the use
of relatively large amounts of sanitizer and other treatment compounds. All
of these, wastes and treatment products, contain solids that accumulate over
time. Add to this the increased evaporation rate in spa/hot tub water and the
result will be a rapid increase in TDS. Keep in mind that as water evaporates,
only the water itself is removed, not the solids it contains. As such the solids
accumulate and reach unacceptable levels faster than in cooler less turbulent
water such as that found in swimming pools.
At elevated levels, TDS can lead to cloudy or hazy water, difficulty in
maintaining water balance, reduction in sanitizer activity and foaming.
Unfortunately, the only way to reduce TDS is to drain the water and
replace it with fresh water.
It is suggested that a residential spa/hot tub be drained and refilled every
three to four months. This is only a general recommendation and actual
frequency of water changes will depend upon how heavily the unit is used and
the treatment program followed. It is often said that when one experiences
unusual problems in managing the water, it is easier and less costly to drain
and refill than to keep trying to make corrections.
19Chapter Three – Biological Factors
CHAPTER THREE - BIOLOGICAL FACTORS Notes:
Disinfection and shock treatment (control of bather waste)
are the key elements in maintaining clean
sanitary spa/hot tub water. The previous two chapters dealt
with keeping the water clear, while here we will
address how to keep it healthy and clean.
I. DISINFECTION
The process of controlling bacteria and viruses in the water to assure the
water will be healthy and safe for bathing is known as disinfection, or
sometimes sanitization. This is a critical process in a spa/hot tub as the water
temperature along with the aeration make this water an ideal environment
for the growth of harmful bacteria. Add to the ideal growth temperature the
heavy bather wastes that will place stress on the sanitizer used and one
has all the ingredients needed to bring about explosive growth potential for
undesirable microorganisms. This section will describe in detail what you need
to know to keep your customers’ water in clean and healthy condition for
bathing.
As we have come to understand, the bather leaves behind a lot of organic
waste in the water. But the bather is also the source of the bacteria that
contaminate the water. In fact the bather is the primary contaminant of
spa/hot tub water. If the cover were to remain in place most spa/hot tub
water would remain clean almost indefinitely. It is most important to control
both the microorganisms and waste products after bathing is completed. In
doing so we control the populations of these organisms while they are at
their lowest numbers. If we do not control them now with a proper sanitizer
residual they can grow and multiply using the wastes left by the bathers as a
food source. If they grow to large numbers they become a very real threat of
disease to the next bather who enters the tub. However, if they are destroyed
when the bathing experience is completed and a cover is put in place, the
water will stay clean and clear ready for the next use.
While a wide variety of methods for disinfecting or sanitizing spa/hot tub
water are available in the market, the two most common methods are Chlorine
and bromine. Over the recent past, other processes have also gained more
attention. These include PHMB (biguanide), Ozone and Ionizers. Each has its
strengths and weaknesses.
CHLORINE
The most commonly recognized sanitizer is Chlorine, but it is not always
the sanitizer of choice for use in spa/hot tub water. While available in a
number of forms any of which could be used the most dominant form for
this application is a granular form commonly known as Dichlor. Dichlor is
white granular compound containing 56-62% available Chlorine. This means
that for every one pound of Dichlor added to water 0.56-0.62 pounds of
actual Chlorine will be present. In addition Dichlor contains cyanuric acid
that is important in outdoor pool use where the cyanuric acid helps keep the
20 Chlorine stable in the presence of sunlight. While the cyanuric acid is of littleChapter Three – Biological Factors
value in outdoor or indoor spa/hot tub water it is of no harm either. What Notes:
makes this form of Chlorine the best for spa/hot tub use is that it is virtually
neutral in pH. Given the rather small water volume and demand for heavy use
the neutral pH avoids unnecessary upsets to water balance.
Once the Chlorine has been added to the water, it can take several different
forms, not all of which are desirable. The following sections on Free Chlorine,
Combined Chlorine and Total Chlorine will address these different Chlorine
forms in depth.
FREE CHLORINE
Free Chlorine is the most desirable form and is the form responsible for
the actual disinfection activity in the water. It is measured using a Free
Chlorine test kit or test strips and its level is critical in the water. If this
form is not present, little or no sanitizing can take place. Free Chlorine is
actually composed of two types of compounds: HOCl (hypochlorous acid) and
OCl¯ (hypochlorite ion). This is important because they exist together in a
condition or state known as equilibrium. This means that together they make
up 100% of the Free Chlorine content, but that content consists of some of
each. For example, if 25% of the Free Chlorine is HOCl, then the OCl¯ level
will be the other 75%. It is important to note that only the HOCl component
is effective as a sanitizer. Therefore, it seems logical that we would want as
much of the Free Chlorine as possible to be in the form of HOCl. However,
the level of HOCl and OCl¯ present is dependent upon the pH. This is one of
the critical reasons that the proper pH level in the water is so important. As
the pH goes up or down, the relative amount of HOCl vs. OCl¯ also increases
or decreases. The following chart shows how much of each of these two
compounds are present at different pH levels.
pH %HOCl %OCl¯
6.0 97 3
7.0 75 25
7.5 50 50
8.0 23 77
9.0 3 97
As the chart shows, at pH 7.5, only about half of the Free Chlorine exists in
the desirable form of HOCl. The level of HOCl will increase as the pH goes
down and it must also be pointed out that as the pH decreases, so does the
stability of the Chlorine. As pH rises, the stability of the Free Chlorine will
increase, but its activity as a sanitizer diminishes. In order to get the most
effective and economic benefit of Chlorine, keep the pH in the desirable
range of 7.2-7.8. Lower pH will be detrimental to equipment and make it more
difficult to maintain a sufficient level of Free Chlorine, while higher pH levels
will render Chlorine ineffective as a sanitizer and increase scaling conditions.
COMBINED CHLORINE
Free Chlorine is highly reactive, and once added to water, quickly attacks
bacteria as well as bather and other wastes. When this occurs, the Chlorine is
21
no longer considered Free Chlorine but rather its form has changed and is nowChapter Three – Biological Factors
referred to as Combined Chlorine. Bather and other wastes are largely made Notes:
up of ammonia-type compounds and related nitrogen based wastes. For this
reason, Combined Chlorine is also referred to as chloramines for the nitrogen
portion of the compound. Combined Chlorine is very stable, but has little or
no sanitizing ability. Not only is Combined Chlorine a very poor disinfectant,
it is the agent responsible for eye burn and skin irritation and results in
the unpleasant Chlorine odor often referred to as a pool with “too much
Chlorine.” It is therefore critical for bather health and comfort that Combined
Chlorine be controlled and kept to a minimum. It is preferable that Combined
Chlorine levels are kept to a maximum of 0.2 ppm. This can be a challenging
task in spa/hot tub maintenance given the larger amounts of waste and
increased dosages of Chlorine required as a result.
TOTAL CHLORINE
Total Chlorine is the sum of the Free Chlorine and Combined Chlorine levels.
Total Chlorine can be measured using most test kits and some test strips. To
determine the Combined Chlorine level, first measure the Free Chlorine level
and then the Total Chlorine level and then subtract the Free Chlorine reading
from the total reading. The difference in values is the Combined Chlorine
level.
HOW TO USE CHLORINE TO SANITIZE WATER:
If you prefer to use Chlorine for sanitizing the water, granular Dichlor is
best. This form will provide a reliable and easy to use source of concentrated
Chlorine.
To use:
1. Add 1/2oz for each 500 gallons of water prior to bathing.
2. Test water to be certain 2-3 ppm residual is present.
3. Shock-oxidize the water with a buffered non-Chlorine shock after
bathing. (See Shock Treatment Section)
Note: Shock-oxidation treatment will destroy the organic bather
waste.
BROMINE
Chlorine and bromine are both members of the same chemical family known
as Halogens. While not as well known as Chlorine, bromine has gained
wide acceptance as a sanitizer, especially in spa/hot tubs. The heavy waste
accumulation places a stress on Chlorine resulting in odors and irritation
due to the build up of Combined Chlorine. Bromine does not suffer from
this problem. Bromine has become a dominant sanitizer for spa/hot tub
applications because users do not experience problems of odors and skin
irritation as they often do with Chlorine sanitizer. In addition bromine is far
less pH dependent than is Chlorine.
When added to water, bromine forms hypobromous acid (HOBr) similarly to
the hypochlorous acid formed by Chlorine. However, unlike Chlorine, the
amount of hypobromous acid is less dependent on pH. The chart below shows
how much more of the active species of HOBr is present over the same pH
22 ranges in comparison to HOCl formed when Chlorine is used.Chapter Three – Biological Factors
pH %HOCl %HOBr Notes:
6.0 97 100%
7.0 75 99%
7.5 50 94%
8.0 23 83%
9.0 3 30%
In addition to bromine activity working over a wider pH range than Chlorine
there are other reasons that tend to favor its use in spa/hot tub water. The
same waste products that place such a stress on Chlorine to result in the
undesirable Combined Chlorine compounds also react with free bromine to
form combined bromine in the water. However, unlike Combined Chlorine
these combined bromine compounds do not cause eye and skin irritation
or foul odors. But of greater advantage, the combined bromine is a very
effective sanitizer virtually equivalent to free bromine. For this reason, it is
not necessary to test for both free and combined bromine. Only a test for
total bromine is needed. Since spa/hot tub water frequently contains heavy
accumulations of waste products, a sanitizer such as bromine that does not
cause adverse skin reactions or odors, or suffer from reduced effectiveness, is
of real advantage.
Bromine is available in three basic forms: tablets, caplets or as a two product
system. Bromine tablets or caplets are usually applied through some type of
feeder device either in-line or a floater-type feeder. The two-product system
relies upon the addition of small amounts of an inert sodium bromide salt,
which by itself does little. The water is then treated with an oxidizer specially
suited for this purpose. The oxidizer acts to convert the sodium bromide into
free bromine. The two-product system has the advantage of reacting in the
water to both control bacteria and oxidizes to destroy waste products in a
single step. These will be discussed in more detail in the section below on
how to use bromine.
HOW TO SANITIZE WITH BROMINE:
There are two distinct means of using bromine to sanitize spa/hot tub water.
The first is with brominating tablets or caplets. These contain a combination
of different bromine sanitizing compounds and are designed for use in a
feeder system either in-line or more commonly in a feeder type that floats on
the surface of the water. They slowly dissolve over time gradually releasing
the bromine sanitizer to maintain a desired bromine level in the water. When
used in this way these tablets will provide continuous bromine residual in the
water for an extended period of time.
23Chapter Three – Biological Factors
To use: Notes:
1. Add a suitable number of tablets to a feeder and adjust the feeder per
manufacturer directions.
2. Test bromine level daily to a residual of 2-4 ppm.
3. It is best to shock-oxidize the water after bathing using a
non-Chlorine shock. This will destroy the organic wastes added by the
bathers.
A second means of sanitizing with bromine is by using the two-product
system. This type of system is different from other sanitizing systems and
holds several advantages. The first product consists of a solution of a simple
salt called sodium bromide, a natural constituent of seawater. This is added
to the spa/hot tub water initially and then weekly thereafter. When added
the sodium bromide does nothing by itself. However, when a buffered
non-Chlorine shock oxidizer is added, it will oxidize the sodium bromide to
result in producing active bromine sanitizer in the water. It is only after the
non-Chlorine shock-oxidizer is added to the water that a sanitizer is actually
present in the water.
Using the system could not be easier as you only need to add the
non-Chlorine shock-oxidizer after bathing is done. One of the advantages then
is that the bather using the tub is not exposed to any sanitizer while actually
bathing. However, when the shock oxidizer is added to the water after
bathing two critical things happen at the same time. Firstly, the production
of bromine sanitizer as stated above destroys any microorganisms left behind
by the bather. Secondly, the non-Chlorine shock oxidizer contains enough
oxidizer to make both the active bromine sanitizer and provide the needed
shock treatment to destroy organic wastes left behind by the bather. In one
single step the two key requirements for clean spa/hot tub water are met. The
time to add the shock oxidizer is after one is finished bathing. After exiting
simply add the required dose and put the cover in place. The water will be
fresh and clean ready for the next bather.
To use:
1. When the tub is first filled add the sodium bromide salt solution to
the water.
2. Turn on filtration system to mix.
3. Add 2 ounces of buffered non-Chlorine shock-oxidizer for each 250
gallons of water.
4. Thereafter simply add non-Chlorine shock-oxidizer after each
bathing period and put cover in place.
5. Weekly add 1 ounces of sodium bromide salt solution for each 250
gallons of water.
24You can also read
